Dispersion types of fibers

12

1. Material dispersion refers to the pulse broadening, which is a result of the phenomenon that the refractive index of fiber material varies according to the light source frequency and different light source frequencies are propagated at different group velocities.
2. Waveguide dispersion is due to the modular propagation constant changes based on wavelengths. It is related to the fiber waveguide structure parameters and the waveguide dispersion values are similar to material dispersion values. Material dispersion and waveguide dispersion are present in both single-mode fibers and multi-mode fibers.
3. Modal dispersion refers to the pulse broadening, which is a result of the phenomenon that the group velocities of the same light source frequency in different transmission modes are different. Modal dispersion mainly exists in multi-mode fibers.
In a word, both material dispersion and waveguide dispersion are caused by different frequencies of transmission signals in a fiber; modal dispersion is caused by different modes of transmission signals in a fiber.

Other related questions:
Dispersion differences between the G.652D fiber and other types of G.652 fibers
Question: What are the dispersion differences between the G.652D fiber and other types of G.652 fibers? Analysis: None Answer: The G.652 fiber is known as a non-zero-dispersion shift fiber (NZ-DSF). Currently, it is the most widely used fiber. The G.652 fiber has low attenuation and zero dispersion at 1310 nm operating wavelength and the lowest attenuation but a larger positive dispersion at 1550 nm operating wavelength. The ITU-T further classifies the G.652 fiber into four types: G.652A, G.652B, G.652C, and G.652D. The dispersion coefficients of these fibers are almost the same. 1. G.652A fiber Before the
  • ITU-T Recommendation G.652
  • released, the G.652A fiber had the parameters most similar to those of the G.652 fiber (in the 1996 edition). This is because the ITU-T recommendation (including the 2000 edition) had no requirements on the polarization mode dispersion (PMD) performance of the G.652A fiber. It should be noted that the 2003 edition made requirements on its PMD. In the past, the highest transmission rate of the G.652A fiber was 2.5 Gbit/s. Now, it can reach 400 km transmission distance in a 10 Gbit/s system, 40 km in a 10 Gbit/s Ethernet system, and 2 km in a 40 Gbit/s system. The G.652A fiber supports the following information: SDH transmission system specified by the ITU-T G.957 STM-16 single-channel SDH transmission system that has an OA, as stipulated in the
  • ITU-T Recommendation G.691
  • 40 km transmission distance in a 10 Gbit/s Ethernet system 40 Gbit/s transmission rate specified by the ITU-T G.693 2. G.652B fiber Compared with the G.652A fiber, the G.652B fiber extends the attenuation requirements to the L band (1625 nm) and requires a lower PMD. The G.652B fiber can reach over 3000 km transmission distance in a 10 Gbit/s system and 80 km transmission distance in a 40Gbit/s system. The G.652B fiber supports the following information: SDH transmission system specified by the ITU-T G.957 STM-64 single-channel SDH transmission system with OA capabilities specified by the ITU-T G.691 STM-64 WDM system with OA capabilities specified by the ITU-T G.692 STM-256 application specified by the ITU-T G.693 and G.959.1 3. G.652C fiber The G.652C fiber is known as a low water peak or MAN-dedicated fiber. It eliminates loss peak (also called water peak) absorbed by the OH root ions near 1385 nm wavelength, which flattens the loss spectrum and adds 125 wavelength channels with a channel spacing of 100 GHz. The G.652C fiber has the similar attribute and application range with those of the G.652A fiber. However, the G.652C fiber has lower attenuation at 1550 nm wavelength. It can be used for the extended band (E band) and short band (S band) in the range of 1360-1530 nm, which expands the available wavelength range and increases the number of WDM channels. It is a good choice for MAN application.4. G.652D fiber The G.652D fiber integrates the advantages of the G.552B and G.652C fibers. It has the similar attribute and application scope with those of the G.652B fiber and requires the same attenuation with that of the G.652C fiber. The G.652D fiber can be used in the range of 1360-1530 nm (E band and S band) wavelengths. It has bright prospects in the MAN application. For details, see the
  • Recommendation ITU-T G.652
  • . Suggestion and conclusion: None

    Dispersion compensation for hybrid use of G.652 and G.655 fibers.
    The G.652 and G.655 fibers have different dispersion coefficients. The dispersion coefficient of the G.652 fiber is 17 ps/nm.km, and the dispersion coefficient of the G.655 fiber is 4.517 ps/nm.km. When the G.652 and G.655 fibers are used together, the dispersion should be calculated respectively. The G.652-specific DCMs can be used to compensate for the dispersion of both G.652 and G.655 fibers. You can divide the length of the G.655 fiber by 4, and then determine the DCM type based on the calculation result.

    Dispersion compensation.
    Question: The G.652 fiber requires 10-30 km reserved in the WDM system. However, some G. 652 fibers require full or over dispersion compensation. Why? Analysis: None Answer: The dispersion is related to the chirped return-to-zero (CRZ) or non-return-to-zero (NRZ) code instead of the advanced forward error correction (AFEC). For a 40-channel system using common code patterns, the G. 652 fiber requires 10-30 km reserved in the WDM system. For super CRZ, the relative dispersion compensation of each span should be in the range of 10 km. The G.655 and G.652 fibers share the same compensation principles. The super WDM dispersion compensation follows the following principles: The super WDM introduces a specific dispersion tolerance. The dispersion compensation should try to control the self-phase modulation (SPM) generated by lines and cancel light source chirp, receiving narrow spectrum in the receive end. In this way, the nonlinear effect will not cause a serious system penalty. The receive-end bit error rate (BER) performance is good. The sideband of the spectrum disappeared. A maximum dispersion tolerance of -300 ps/nm to +500 ps/nm can be obtained. Dispersion compensation principles: 1. Select proper dispersion pre-compensation. 2. Use distributed compensation and control the accumulated dispersion values of optical signals at each incident location to control the SPM effect of optical fibers. Different optical fibers have different nonlinear effect and dispersion. Therefore, the nonlinear effect and dispersion observe different compensation principles. G.655 fiber dispersion compensation principles: 1. The G.655 fiber is over-compensated by 40 km, and under-compensated by 80 km. (An OSNR penalty no greater than 1 dB is introduced.) 2. The dispersion pre-compensation value depends on the number of spans. If the number of spans is greater than or equal to six and less than or equal to 11, the G.655 fiber is pre-compensated for 20 km. If the number of spans is greater than 11, the G.655 fiber is not pre-compensated. 3. The relative compensation dispersion value of each span is within 10 km. The relative dispersion compensation value should be offset if possible. That is, the incident dispersion of each optical line amplifier (OLA) station must be within the range of -10 km minus the pre-compensated dispersion to 10 km minus the pre-compensated dispersion. If 20 km is pre-compensated, the incident dispersion of each OLA station is in the range of -30 km to -10 km. If no pre-compensation is required, the incident dispersion of each OLA site is in the range of -10 km to +10 km. 4: If a span distance is long and out of the compensation range of a DCM module, the G.655 fiber can be under-compensated. (The maximum compensation value can be 160 km.) But the incident dispersion must be compensated in the next one or next two spans following the principle three.) 5. For a regeneration span whose span number is larger than 12, if the first span is long and the dispersion must be pre-compensated, 20 km can be pre-compensated. And the incident dispersion is compensated in the range of -10 km to +10 km in the next one or two spans.

    Types of fibers used to connect the HBA board
    LSH/APC connectors and fibers are used on the OUT port of the HBA board, and LC connectors and fibers are used on the IN port of the HBA board.

    If you have more questions, you can seek help from following ways:
    To iKnow To Live Chat
    Scroll to top